Grass mowing machines used for golf courses, parks, and athletic fields where a high quality of cut is desired, may include one or more cutting units. For example, each cutting unit may be a reel mower having multiple spiral cutting blades rotating in close proximity to a bedknife. Each cutting unit may be mounted to the grass mowing machine using a cutting unit mounting device or coupling mechanism through a yoke which may be a tubular element with a crossbar that extends laterally over and is attached to the left and right sides of the cutting unit. The cutting unit mounting device may include a pivoting mechanism to allow the cutting unit to pivot on multiple axes to cut grass on humps, slopes and other irregular surfaces without damaging the surfaces. The cutting unit mounting device should allow the cutting unit to pitch (front to back pivoting) and yaw (side-to-side pivoting). Additionally, the cutting unit mounting device should allow the cutting unit to pivot or steer on a vertical axis during a turn. This helps minimize the tendency of the cutting unit to drag, scuff or otherwise damage the turf during mowing. If several cutting units are carried by a vehicle, each cutting unit mounting device may be attached to the end of a lift arm that may pivot to allow the cutting unit to move up and down over the ground surface, while applying down pressure to the cutting unit.
The cutting unit mounting device also may allow the cutting unit to be raised from a mowing position to a transport position, and rotated to a service position. For example, U.S. Pat. No. 5,343,680 assigned to Deere & Company relates to a suspension mechanism for reel mowers allowing the operator to easily access the underside of cutting units for service, while remaining connected to the lift arms. A swing out feature is provided and includes a knuckle joint mechanism which allows the cutting units to swing downwardly when the lift arms are raised to a service position. The undersides of the cutting units are exposed forwardly or to the side for allowing an operator to service the cutting units. The knuckle joint mechanism helps the operator easily switch the vehicle between its mowing mode and its service mode. The knuckle joint secures the cutting unit in a relatively rigid position when the cutting unit is exposed for service.
U.S. Pat. Nos. 5,293,729, 5,297,378 and 5,459,984 assigned to Deere & Company, and U.S. Pat. Re. No. 34,921 assigned to The Toro Company, provide examples of grass mowing machines for golf courses having cutting unit mounting devices for reel mower cutting units.
Existing cutting unit mounting devices are relatively expensive and complex, and have a relatively high parts count, which can contribute to the cost and assembly time of the grass mowing machine. There is a need for a lower cost, simplified cutting unit mounting device that allows the cutting unit to pitch, yaw and steer during mowing, and that allows the cutting unit to be easily moved from a mowing position to a transport position, and rotated to a service position. There also is a need for a cutting unit mounting device that minimizes any damage to the turf as the raised cutting unit is lowered down to the mowing position.
Cutting unit mounting devices may include ball joints for connecting cutting units to lift arms. To manufacture the ball joint, it is necessary to slide the ball over a tubular element. Then, the tubular element may be bent or welded into a U-shaped yoke including a crossbar extending laterally over and attached to the left and right sides of the cutting unit. Before the yoke assembly can be painted, the ball must be masked to prevent paint buildup from interfering with the proper fit between the ball and its housing. After painting, the masking must be removed before assembly of the ball in the ball housing. The ball then must be located and positioned on the yoke using a pin which is inserted in and through a hole drilled through both the ball and the tube. Each of these steps are time consuming and costly. Additionally, the ball does not have a protective finish so it may readily rust in the corrosive environment where grass mowing machines operate. There is a need for an improved ball joint for a cutting unit mounting device, and an improved method for manufacturing a ball joint for a cutting unit mounting device, that will reduce cost and time, and improve quality.